Conservation status of Rorippa calycina (persistent-sepal yellowcress) in Montana

s

639.99
Nllcsr
2001

Conservation Status of

Rorippa calycina

(persistent-sepal yellowcress)

in Montana

Prepared for:

U.S. Fish and Wildlife Service
Under SE-5P Segment 11

Prepared by:

STATE DOCUMENTS COLLECTION

"lAY 1 ;3 2001

MONTANA STATE LIBRARY

1515 E. 6th AVE.
HELENA, MONTANA 59620

Bonnie Heidel

Montana Natural Heritage Program

1 5 1 5 E. Sixth Avenue

Helena, MT 59620-1800

March 2001

j W^ MONTANA

__i) Natural Heritage

MONTANA STATE LIBRARY

3 0864 0015 6141 7

Conservation Status of

Rorippa calycina

(persistent-sepal yellowcress)

in Montana

© 2001 Montana Natural Heritage Program

State Libran,' Building • P.O. Box 20 1 800 • 1 5 1 5 East Sixth Avenue • Helena, MT 59620- 1 800 • 406^44-3009

This document should be cited as follows:

Pleidel, B. 2001 . Conservation status oi' Rorippa calycina (persistent-sepal yellowcress) in
Montana. Report to the U.S. Fish and Wildlife Service. Montana Natural I Icritage Program,
Helena. 10 pp.

EXECUTIVE SUMMARY

Rorippa calycina (persistent-sepal yellowcress) is
a regional Great Plains endemic that has been
recorded at 23 sites in Wyoming, and a total of 5
historic or extirpated sites in Montana and Nortli
Dakota. It was a former candidate for listing under
the Endangered Species Act until the candidate
program was discontinued in 1996.

During this study, over 1 50 miles of riparian
habitat and 6 reservoirs were surveyed in the
areas of the known records, representing the
historic range of Rorippa calycina in Montana.
These surveys did not relocate the species. One
of the 5 Montana collection records was found to
be based on a misidentified specimen. The state

rank of Rorippa calycina in Montana remains at
S 1 with the expectation that Wyoming's Yellowtail
Reservoir population may extend into the state.

This species' long-term viability hinges on existing
Wyoming populations, most of which are associ-
ated with the artificial conditions of reservoirs
rather than free-flowing rivers. These are consid-
ered relatively secure barring detrimental water
management changes and noxious weed en-
croachment. This report and the most current
Wyoming status report (Fertig and Welp 1 998)
are to be used together as references on the
species status in Montana and pertinent aspects of
its biology.

ACKNOWLEDGEMENTS

We thank Cathie Jean. Jack Greenlee, Susan
Rinehart, and Mike Erwin for their paddling and
help on the surveys. Cedron Jones graciously
provided use of his canoe. Ronald Hartman (RM)
reviewed and annotated the Choteau County
voucher specimen. Special thanks are extended to
Walter Fertig. Wyoming Natural Diversity Data-
base, for a copy of the Wyoming status report on
Rorippa calycina, for providing most of the
current information and discussion on Rorippa

calycina in a joint Bighorn Canyon National
Recreation Area rare plant report, and for interest-
ing discussions on the species. The report was
reviewed, edited and produced with the help of
Joy Lewis, Sue Crispin, and Katrina Scheuerman.
This work was supported by a Section 6 grant
agreement between the U.S. Fish and Wildlife
Service and the Montana State Library - Montana
Natural Heritage Program.

TABLE OF CONTENTS

I. INTRODUCTION ]

II. METHODS 1

III. SPECIES INFORMATION 2

A. CLASSIFICATION 2

B. PRESENT LEGAL OR OTHER FORMAL STATUS 2

C. DESCRIPTION 3

D. GEOGRAPHICAL DISTRIBUTION 4

E. HABITAT 6

F. LAND OWNERSHIP 8

IV. ASSESSMENT AND MANAGEMENT RECOMMENDATIONS 8

A. POTENTIALTHREATS TO CURRENTLY KNOWN POPULATIONS: 8

B. MANAGEMENT PRACTICES AND RESPONSE: 8

C. CONSERVATION RECOMMENDATIONS: 9

D. STATUS RECOMMENDATIONS: 9

E. INTERPRETATION OF SURVEY RESULTS TO DATE: 9

V. LITERATURE CITED 10

Tables and Figures

Table 1 . Heritage Rank Definitions

Table 2. Rorippa calycina survey areas in Montana

Figure 1 . Illustration of Rorippa calycina

Figure 2. Photograph of Rorippa calycina

Figure 3. Rorippa calycina distribution in Montana, North Dakota and Wyoming

I. INTRODUCTION

Rorippa calycina (persistent-sepal yellowcress)
was first discovered by F. V. Hayden in 1 854
along the Yellowstone River upstream from Miles
Cit>' near the historic site of Fort Sarpy (Sheffield).
Montana. Two more collections were made
before the turn of the century on or near the
Missouri and Yellowstone Rivers in Montana, and
one was made immediately downstream in North
Dakota. The fact that Rorippa calycina was only
known from four historic collections provided tlie
basis for recommending that the species be
considered for listing as threatened under the
Endangered Species Act (Ayensu and DeFilipps
1978).

tage Program (MTNHP) to systematically survey
for the species in Montana and evaluate its status.
This report and the most current Wyoming status
report (Fertig and Welp 1 998) are to be used
together as references on the species status in
Montana and pertinent species biology.

This study was conducted by the Montana Natural
Heritage Program (MTNHP), which collects,
maintains and provides statewide information on
features of biological significance, including species
of special concern and natural vegetation.
MTNHP serves as a clearinghouse, assembling
information from secondary sources such as
museum specimens, published articles, and reports
and supplementing it with field studies.

In Wyoming, Rorippa calycina was first discov-
ered in 1 977, and concerted surveys documented
a total of 23 occurrences. Most of these are
restricted to reservoir margins, and Wyoming
botanists consider it secure in the state, based on
the presumption that it can persist in reservoir
settings. (Lichvar 1981, Fertig and Welp 1 998). It
was also collected in the Northwest Territories
(Mulligan and Porsild 1 966), 2500 km from its
nearest known station, presumably dispersed by
waterfowl (Rollins 1993).

There has been no statewide survey for the
species in Montana or North Dakota, but two
new Montana collection records were added by
botanists doing consulting work in 1 980 and
1 990. One of the collection sites is a stock pond.
This site was resurveyed and the species is con-
sidered extirpated (Heidel 1 994). The other new
record was based on a specimen that was
misidenfified, as determined in the course of this
study.

Survey of this species was identified as a priority
in Montana because it was known only from
historic or extirpated records collected from areas
that remain some of the most extensive free-
fiowing river habitat in the species' range. In 1 999,
the U.S. Fish and Wildlife Service provided
Section 6 support to the Montana Natural Heri-

II. METHODS

The author conducted field surveys in 1 999-2000
to relocate the species in the four river reaches
where it has been collected. The fifth collecfion
was from a stock pond and was resurveyed in
1 993 (Heidel 1 994) and is considered exfirpated.
In addition to resurveyed areas, 3 other Missouri/
Yellowstone River reaches and 6 reservoirs with
potential habitat were surveyed. This included the
lower Yellowstone River, immediately upstream
from the single historic collection site in North
Dakota.

We used information on the known distribution of
Rorippa calycina in Montana, which had previ-
ously been compiled from herbarium records by
MTNHP in the 1 980's and integrated in MTNHP
statewide data resources and references (e.g.,
Lesica and Shelly 1 99 1 ). The following herbaria
house the 5 specimens o{ Rorippa calycina from
Montana: Montana State University. University of
Montana, and Missouri Botanical Garden. Infor-
mation on the habitat and status elsewhere was
obtained from scientific literature and knowledge-
able individuals.

In preparation for survey, sandy shoreline sites
were identified and mapped with tlic help of

BLM land status maps (1 : 1 00,000), along with
aerial photos in select cases. Fieldwork was
conducted between 7 July - 22 Oct. The pres-
ence of other species ofRorippa in fruit indicated
suitable phenology for identification of the rare
species. The species flowers from late May to
August, although blooming may extend into
October under favorable circumstances. Since
phenology and shoreline access depends on water
levels, and finits are needed for verification, most
of our survey was conducted after river flows had
peaked. At each site, notes were taken on the
dominant species, the Mustard Family species
present, and the substrate texture at the water's
edge.

within the genus. Stuckey (1972) considered
Rorippa calycina to be most closely related
to R. columbiae (syn. R. calycina var.
columbiae) and R. subumbellata, 2 other
localized endemics of the Columbia River and
Lake Tahoe areas, respectively. According to
Stuckey. all 3 represent old, relic species and
the only survivors of a formeriy more wide-
spread and morphologically variable complex.
Among Montana species. Rorippa calycina is
most closely related to R. sinuata (Stuckey
1972).

B. PRESENT LEGAL OR OTHER FOR-
MAL STATUS

Other state species of special concern were
documented on Plant Species of Special Concern
survey forms, mapped, and photographed.

III. SPECIES INFORMATION
A. CLASSIFICATION

1 . SCffiNTIFIC NAME; Rorippa calycina

(Engelm.)Rydb. (Rydberg 1900; Stuckey
1972).

2. SYNONYMS: Nasturtium calycinum
Engelm. (Warren 1858)

3 . COMMON NAMES : persistent-sepal
yelllowcress

1. NATIONAL

a. LEGAL STATUS : Rorippa calycina was
formerly a C2 candidate for listing under the
Endangered Species Act (US Fish and Wild-
life Service 1993). The C2 list included
species that might have warranted listing as
Threatened or Endangered, however, FWS
lacked sufficient biological data to support a
listing proposal. In February 1 996, FWS
revised its candidate policy and eliminated the
C2 designation. As a result Rorippa calycina
currently has no legal status.

b. HERITAGE RANK: Definitions for global and
state ranks are given in Table 1 .

2. STALE

4. FAMILY: Brassicaceae or Cruciferae (Mus-
tard Family)

5. SIZE OF GENUS: Rollins (1993) recognizes
approximately 75 species in this genus world-
wide, wdth 29 species occurring in North
America. Dom ( 1 984) recognizes eight
species in Montana.

6. PHYLOGENETIC RELATIONSHIPS.-
Rorippa calycina is one of 6 species in
Section Sinuatae, the most primitive group

a. MONTANA

L LEGAL STATUS: None.

ii HERITAGE RANK: Rorippa calycina is
ranked S 1 in Montana, indicating that it is
critically imperiled because of extreme rarity,
based on one recent record that is considered
extirpated. 3 historic records, and the strong
likelihood of one Wyoming population cross-
ing the state line.

c. NORTH DAKOTA d. WYOMING

L LEGAL STATUS: None, i. LEGAL STATUS: None

i i HERITAGE RANK: Rorippa calycma is ii. HERITAGE RANK: Rorippa calycina is

ranked SH in North Dakota, reflecting that ranked S3 in Wyoming, indicating that it is rare or

this species in known only from one historic local throughout its range or found locally in a

record in the state. restricted range in the state.

Table 1. HERITAGE PROGRAM RANK DEFINITIONS

Taxa are evaluated and ranked by the Heritage Program on the basis of their global (range-wide) status,
and their state-wide status according to a standardized procedure used by all Natural Heritage Programs
( The Nahare Conservancy 1 992 ). These ranks are used to determine protection and data collection
priorities, and are revised, as new information becomes available.

For each level of distribution — global and state— species are assigned a numeric rank ranging from 1
(critically imperiled) to 5 (demonstrably secure). This reflects the species' relative endangerment and is
based on the total number of occurrences, as conditioned by degree of habitat threat, geographic
distribution pattems and population size and trends. General ranking standards are summarized below.

RANK/DEFINITION

1 Critically imperiled because of extreme rarity (usually 5 or fewer occurrences, or very few
remaining individuals), or because of some factor of its biology making it especially vubierable to
extinction.

2 Imperiled because of rarity (usually 6 to 20 occurrences), or because of other factors demon-
strably making it very vulnerable to extinction throughout its range.

3 Vulnerable because of rarity ( usually 2 1 to 1 00 occurrences) or found in a restricted range even
though it may be abundant at some of its locations.

4 Apparently secure, though it may be quite rare in parts of its range, especially at the periphery.

5 Demonstrably secure, though it may be quite rare in parts of its range, especially at the periph-
ery.

U Possibly in peril, but status uncertain, more information needed.

H Historical, known only from records over 50 year ago, may be rediscovered.

X Believed to be extinct; historical records only

C. DESCRIPTION

1 . GENERAL NON-TECHNICAL DESCRIP-
TION: Persistent-sepal yellowcress is a
rhizomatous short-lived perennial herb with
upright or spreading stems 1 0-40 cm tall The
stems and foliage are pubescent throughout
with stiff, unbranched hairs. Stem leaves are
pinnately divided or wavy-lobed, sessile, and
2.5-5 cm long. The flowers are borne in
terminal and axillary inflorescences and have 4
yellow petals 3-5 mm long and 4 sepals that
persist in fruit. Fruits are ovoid to nearly
globose, 2-4 mm long, and conspicuously
pubescent with unbranched hairs that are
broadest at the base. Styles in fruit are 1 -2
mm long and glabrous ( Stuckey 1 972;
Hitchcock etal. 1964; Dom 1984; Rollins
1993; Fertig et al. 1994; Fertig and Welp
1998, Heidel and Fertig 2000).

2. SIMILAR SPECIES : Rorlppa simiata has
elongate, glabrous fruits over 5 mm long,
deciduous sepals, and round, glassy, ball-like
hairs on the leaves. R. curvipes often has
white petals, finely hairy sepals, deeply
pinnate leaves and glabrous to sparsely hairy
fruits and leaves. All other Montana and
Wyoming species of Rorlppa are taprooted
annuals or biennials with longer, more erect
stems and fruits that are
either round or narrowly
elongate (Fertig and Welp
1998).

Figure 1. Illustration of Rorippa calycina by Jane
L. Dom from 'Wyoning Rare Plant Field Guide'

Figure 2 I'holo ol Kanppa calycina by Jennifer Whipple

D. GEOGR4PHICAL DISTRTOUTION

1 . RANGE : Rorippa calycina is a regional
endemic that has been documented in Mon-
tana, western North Dakota, and central
Wyoming. Waterfowl carry its seeds, and one
disjunct population was documented 2,500
miles to the north on the Arctic coast of
Canada's Northwest Territories (Mulligan and
Porsild 1966). In Montana, it was known
from the Missouri and Yellowstone River
drainages, including historic records from
Cascade, Custer and Yellowstone counties,
and a recent record from McCone County
that is probably extirpated (Heidel 1994). We
determined that a voucher specimen collected
from Choteau County, Montana had been
misidentified . The exceptional intactness of
the Choteau County collection site and pres-
ence of other Rorippa species prompted
examination of the voucher specimen. It was
sent off for annotation by Ronald Hartman
(RM) and redetermined to be R. sinuata.
Thus, there are only 4 valid records for the
species in the state, and we have the unusual
circumstance of there being fewer species'
records after surve>- than before. In Wyoming.
Rorippa calycina is known from the Bighorn

Figure 3. Rorippa ca/vcmcr-historic and extant
distribution in Montana, North Dakota and Wyoming

Basin, North Platte River drainage, and Great
Divide. Green River, and Wmd River basins in
Albany. Big Horn. Carbon. Fremont. Park.
Sweetwater, and Washakie counties (Fertig
and Welp 1998).

The 4 element occurrence records oi Rorippa
calycina in Montana are submitted with this
report as separate attachments.

2 . EXTANT SITES : There are no known extant
populations in Montana.

HISTORICAL AND EXTIRPATED POPU
LATIONS: Three historic collections were
made in Montana, including its first discovery.
1 854 -Fort Sarpy (Sheffield) on the lower
Yellowstone River (Custer Co., closest
town: Miles City)
1 880 -Between Sun River mouth (Great
Falls) and Fort Benton, on "lakes"; this
location may refer to the Missouri River
but there are few oxbows, and it may also
refer to coulees, the Shonkin Sag lake
system, or Benton Lake. This unmappable
record is in either Cascade or Choteau
counties.
1 890 -Custer Station, on or adjoining the
lower Yellowstone River (Yellowstone
County; closest town: Reedpoint). Note:
This historic place name was located with
the help of the Montana Historical Society.
The county of distribution was previously
held in question (Lesica and Shelly 1 99 1).

The only collection of this species between
1 900-2000 was made in McCone Counrv' in
1 980 along the shores of a stock pond. At the
McCone County site, the plant numbers were
described as "few." It was resurveyed in
1 994 and is considered extirpated (Heidel
1 994). At the start of this study, we also
recognized a Choteau County specimen
collected in 1 990. In the course of this study,
the specimen was reviewed and ruled out as
Rorippa calycina. It was annotated by
Ronald Hartman. and determined to be R.
.S7>7wa/a (Hartman personal communication).

4. PRESENT SITES WHERE STATUS RE-
MAINS UNKNOWN: There is some chance
that the species may occur in Montana in the
Bighom Canyon, just north of the Yellowtail
Reservoir, of Wyoming. However, as the
reservoir flows northward, the topography
changes from an open landscape to a con-
stricted canyon and there is little potential
shoreline habitat in Montana. The species has
been documented in detail on the Yellowtail
Reservoir (Heidel and Fertig 2000). Our
limited Bighom Canyon surveys in August of
1999 were conducted in exceptional
highwater conditions and we were not able to
prove or rule out that it extends into Montana.

5. UNVERIFIED/UNDOCUMENTED RE-
PORTS: None

6. AREAS SURVEYED BUT SPECIES NOT
LOCATED: A summary of field surveys is
presented in Table 2, and cross-referenced in
the report by the area name. Asterisked areas
were surveyed as part of separate projects,
but they included Rorippa calycina as a
target.

Field surveys for this project encompassed the
4 river reaches of historic collections, select
river reaches between historical collections,
reservoirs visited in conjunction with other
surveys, and reservoirs visited incidental to
other travels. Not all potential habitat was
surveyed. The potential habitat of the species,
in river settings, includes all of the fi-ee-flowing
Missouri River below the Dearborn River
mouth, and all of the Yellowstone River below
Greycliff to its mouth on the Missouri River.
The surveys conducted for this project
spanned approximated 20% of the species'
potential riverine habitat in Montana.

7. AREAS OF UNSURVEYED POTENTIAL
HABITAT: The most extensive areas of sandy
riparian shoreline habitat were observed in the
lowermost Yellowstone River between the
towns of Intake and Savage. The lowermost

Yellowstone River may represent the most
extensive unsurveyed potential habitat

Surveys at Deadman Basin and Martinsdale
Reservoirs were too late for effectiveness.
These sites had by far the most extensive
sandy shoreline habitat among the reservoirs
surveyed. In addition, the Bighom Canyon
may also have unsurveyed potential habitat.

The availability of sandy or gravelly shoreline
habitat at Montana's largest reservoir. Fort
Peck Reservoir, seems unlikely but has not
been adequately evaluated.

E. HABITAT:

Rorippa calycina is an early-to mid-succes-
sion species found primarily along moist sandy
to muddy banks of streams, stock ponds, and
man-made reservoirs near the high-water line.
The typical shoreline zone is a broad flat and
includes sandy parent material. Early collec-
tions suggest that its natural habitat is confined
to zones below the highwater mark of Great
Plains rivers. Most populations are in
sparsely- vegetated settings that are semi-
disturbed and annually flooded, located in
small inlets or bays with scattered clumps of
foxtail barley {Hordeumjuhatum),
Sandberg's bluegrass {Poa secunda), western
wheatgrass {Pascopyrum smithii) and a
variety of native or exotic early successional
forbs. Occasionally, plants can also be found
on grassy shores or in openings amid coyote
willow {Salix exigua) or salt cedar ( Tamarix
chinemis) thickets.

The most recent Wyoming status report
(Fertig and Welp 1 998) provides detailed
information on habitat, including associated
vegetation, fi-equently associated species, and
soil relationships. In addition, that report
provides the only available summary of
population biology, demography and popula-
tion ecology.

Table 2. Rorippa calycina survey areas in Montana

AREA

SURVEY
TYPE

BASIS

SCOPE

Fort Sarpy (Sheffield) on

9/14/99

1854coUection

App. 16 miles including

Yellowstone River (Rosebud

shorelines and islands

east to Horton)

7 miles s. of Custer Station (a

7/7/99 to

1890coUection

App. 31 miles including

railroad crossing) on
Yellowstone Rrver (Greycliff

7/8/99

shorelines and islands

east to Columbus)

Between Sun River mouth and

7/2/00

ISSOcoUection

Kingsbury Lake WPA (east

Fort Benton, on "lakes" - it is
unclear whether the collection

shore), Antelope Lake
(drained)

was made on or off the

Missouri River

White Cliffs area on Missouri

7/7/00 to

1990 collection;

App. 47 miles including

River plus Loma bridge (Coal

7/9/00

incorrectly identified

shorelines and islands

Banks east to Judith Landings)

McGuire Creek stock pond*

1993

1980coUection

Reservoir perimeters

Yellowstone River (Captain

9/13/99

Reports indicate sand

App. 19 miles including

Clark FA east to Big Horn FA,

deposits

shorelines and islands

plus Myers FA area)

Missouri Rrver (Pelican Point

9/4/00

Geological maps and

App. 24 miles including

FA east to Dunes FA)

reports indicate extensive
sand deposits

shorelines and islands

Yellowstone River (Intake to

9/30/00 to

Geological maps and

App. 15 miles including

Elk Island, plus Seven Sisters

10/1/00

reports indicate extensive

shorelines and islands

WMA)

sand deposits. This area
is app. 50 miles upstream
from the 1854 collection
site of the species in ND.

Bighorn Canyon*

8/5/99
8/9/99

Occurs immediately
upstream in WY above
the canyon

Sandy inlets and gravel
banks

Cooney Reservoir*

8/10/00

Incidental survey to sand

North side of reservoir on

shores

public land

Deadman Basin Reservoir

10/22/00

Incidental survey to sand

Brief visit at public access,

shores

after frost

Gartside Reservoir

10/1/00

Incidental survey to sand/

Limited exposed shoreline -

gravel shores

both sides

Kuester Reservoir

10/1/00

Incidental survey to sand

East side of reservoir on

shores

public land

Martinsdale Reservoir

10/22/00

Incidental survey to sand

Brief visit at public access.

...shores

aft?r frpst

F. LAND OWNERSHIP:

The only recent record of this species in
Montana was documented on private land,
namely the McCone County collection from a
stock pond setting where the species is
considered extirpated. The precise locations
of the three historic records are not known.
The river valley landscapes in the vicinity of
these areas are primarily privately owned, and
public tracts are few.

IV. ASSESSMENT AND MANAGE-
MENT RECOMMENDATIONS

A. POTENTIALTHREATS TO CURRENT-
LY KNOWN POPULATIONS:

Changes in watershed management could have
important impacts on reservoir populations of
Rorippa calycina in Wyoming. Fluctuating
water levels remain critical for creating and
maintaining the shoreline flats habitat favored
by this plant. Maintaining reservoirs at a
constant level could encourage later succes
sional species to become established and
crowd out Rorippa calycina. Permanently
raising water levels could wipe out existing,
low-lying colonies, but should create new
habitat higher on the bank. Colonization of
such sites, however, could be restricted if
existing seedbanks are eliminated (Fertig and
Welp 1998).

Competition from exotic plants, especially salt
cedar, is a serious threat at several reservoir
sites in Wyoming, including Yellowtail Reser-
voir on Bighorn Canyon NRA. Dense growth
of tamarisk can shade out Rorippa and
stabilize its shoreline habitats (Fertig and Welp
1 998). Spotted knapweed {Centaurea
maculosa) is also present at the margins of
this species' habitat, including a number of
Bighom Canyon NRA public access sites,
though it is not nearly as widespread at this
time as salt cedar. Leafy spurge {Euphorbia
esula) is invading along the Yellowstone River
Weed control efforts, if employed, need to be

planned carefully to ensure that herbicides do
not directly kill Rorippa calycina plants or ■
negatively affect its pollinators. |

Other potential threats include soil compaction
from off-road vehicles in shoreline habitats,
development of shoreline recreational facilities
or access, trampling of plants and their habitat
from high concentrations of livestock and
wildlife, and impacts from pollution associated
with mining (Fertig and Welp 1 998).

Threats to Rorippa calycina parallel those of
a close relative, Rorippa columbiae, which is
listed as threatened. However, the latter is
apparently restricted to free-flowing river
habitat, where it is strongly affected by the
water levels that are regulated by dams (Sauer
and Leder 1 985). Review of reports and
publications on the species biology, ecology
and management of Rorippa columbiae could
yield valuable insights for Rorippa calycina.

B. MANAGEMENT PRACTICES AND
RESPONSE:

Little evidence of grazing or browsing on
leaves or stems of Rorippa calycina exists
according to Wyoming investigators (Fertig
and Welp 1998). They reported, however,
that heavy shoreline trampling affects species'
habitat suitability. Shoreline trampling is the
most likely cause for extirpation at the
McCone County occurrence in Montana
(Heidel 1994).

C. CONSERVATION RECOMMEND-
ATIONS:

See Fertig and Welp (1998)

D. STATUS RECOMMENDATIONS:

This species is thought to have expanded its
habitat in Wyoming with the construction of
new impoundments (Lichvar 1 98 1 . Fertig and
Welp 1998, Rollins 1993). If reservoir occur-
rences are viable over the long term, then
federal status is not warranted for Rorippa
calycina. The apparent absence of this

species in its historic Montana range, including
the free-flowing Yellowstone River, supports
the case for monitoring of populations' status
in Wyoming.

We recommend expansion of survey efforts
for Rorippa calycina in Montana, with the
highest priority in natural habitat on the lowest
reaches of the Yellowstone River. Surveys on
3 reservoir settings are secondary priorities.
The species is likely to extend from popula
tions on the Yellowtail Reservoir. Wyoming
into the Bighorn Canyon, Montana, even
though there is limited potential habitat. We
identified extensive potential habitat on Dead
man Basin and Martinsdale Reservoir in late
October, but it was too late for effective
surveys. A dual-purpose survey for Rorippa
calycina and salt cedar {Tamarix chinensis)
is recommended at the latter 2 reservoirs.
Precise locations of both species should be
documented, for conservation oi Rorippa
calycina and eradication of Tamarix
chiensis.

The lowest priority for survey is on the
Charles M. Russell NWR. Fort Peck Reser-
voir is the largest reservoir in Montana, but it
has limited sandy shoreline habitat. In general.
Rorippa calycina should continue to be
sought during river and reservoir management
studies or studies of riparian vegetation and
plants of concern.

. INTERPRETATION OF SURVEY RE-
SULTS TO DATE:

Though our surveys did not document extant
populations of Rorippa calyina in Montana.

we did document the only recent record in the
state of poison suckleya (Suckleya
suckleyana). another plant species of con
cem, on the lower Yellowstone River. This
species is associated with Rorippa calycina in
Wyoming (Fertig and Welp 1998). We also
documented a new addition to the state flora,
square-stem monkeyflower (Mimulus
ringens) on the Missouri River (Heidel and
Vanderhorst in progress). In addition, we
gathered valuable observations of watch
species and early-succession riparian plant
communities.

The reason(s) behind these negative results
may lie with habitat loss or degradation,
including altered hydrological regime, shore
line trampling, weed invasion (salt cedar, leafy
spurge, spotted knapweed), or their second
ary effects of altering succession. The
reason(s) may also be linked to fluctuating
species numbers; the species" could be
overlooked if numbers were low during the
years of inventory, or during fall surveys, when
it is in fiiiit and less conspicuous.

This study also suggests a dearth of botanical
survey on the Missouri and Yellowstone rivers,
given that we documented new records for
several plant species of statewide significance.
Additional survey for Rorippa calycina will
certainly add to our knowledge of the plants
and plant communities in these riparian sys
terns.

V. LITERATURE CITED

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gered and threatened plants of the United
States. Smithsonian Institution and World
Wildlife Fund, Washington, DC. 403 pp.

Dom, R. D. 1984. Vascular Plants of Montana.
Mountain West Publishing, Cheyenne,
WY. 240 pp.

Lesica,P and J. S. Shelly. 1991. Sensitive.
Threatened and Endangered Vascular
Plants of Montana. Montana Natural
Heritage Program, Helena, MT.

Lichvar, R. W 1 98 1 . Field survey for Rorippa
calycina (Engelm.) Rydb. Report pre-
pared for the Bureau of Land Manage-
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Program. Cheyenne. WY.

Fertig, W 1 994. Wyoming Rare Plant Field
Guide. Wyoming Rare Plant Technical
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Fertig, W. and L. Welp. 1998. Status report on
persistent-sepal yellowcress {Rorippa
calycina) in Wyoming. Report prepared
for the Bureau of Land Management
Wyoming State Office by the Wyoming
Natural Diversity Database, Laramie, WY.

Heidel, B. and W. Fertig. 2000. Rare plants of
Bighom Canyon National Recreation
Area. Report to the National Fish and
Wildlife Foundation and Bighom Canyon
National Recreation Area. Montana
Natural Heritage Program and Wyoming
Natural Diversity Database.

Mulligan. G.A. and A.E. Porsild. 1966. Rorippa
calycina in the Northwest Territories.
Canadian Journal of Botany 44: 1 1 05-
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Rollins. R. C. 1993. The Cruciferae of Continental
North America, Systematics of the Mus-
tard Family from the Arctic to Panama.
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Rydberg, P A. 1 900. Catalogue of the Flora of
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Park. Memoirs New York Botanical
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Sauer,R.H.andJ.E.Leder. 1985. The Status
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Heidel, B. 1 994. Sensitive plant species survey -
Garfield and McCone counties, Montana.
Report to the Bureau of Land Manage-
ment. Montana Natural Heritage Program,
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Stuckey, R. L. 1 972. Taxonomy and distribution
of the genus Rorippa (Cruciferae) in
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Hitchcock. C.L. and A. Cronquist. 1 964. Pt 2.

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